Splitting wood for various purposes is old. Over the years, many different devices for splitting wood have been developed, These devices generally use some sort of means for spreading apart the wood after it has been struck by a cutting edge. Some of the prior art splitting tools are simply wedges in which the sharp end is driven into the wood by striking it with a maul. Others are much more complicated and utilize various arrangements of levers or arms which spread apart the wood. Examples of this latter type of design may be found in U.S. Pat. Nos. 4,044,808, 4,372,360, 4,383,562 and 4,440,205.
U.S. Pat. No. 4,044,808 discloses a splitting tool with a cutting edge flanked by a pair of pivoting spreaders located slightly rearward of the cutting edge. As the cutting edge enters the wood, end surfaces of the spreaders enter the crack formed by the cutting edge and tend to force the two pieces of the wood apart. The wood is split through the initial thrust of the cutting edge followed by contact of the spreaders and the wood.
U.S. Pat. No. 4,372,360 is very similar to U.S. Pat. No. 4,044,808, in that it also discloses a splitting tool with a cutting edge flanked by a pair of pivotable spreaders. In addition, the tool in U.S. Pat. No. 4,372,360 includes a compression spring which transmits striking force to the spreaders, causing the spreaders to enter the wood and force the two pieces apart by a combination of contact with the wood and an applied force from the compression spring.
U.S. Pat. No. 4,383,562 discloses a variation on the scheme of flanking spreaders. In this patent, the splitting tool has a cutting edge made up in part of two spreaders which, unlike the earlier patents, have an edge which enters the wood simultaneously with a non-pivotable cutting edge. The spreaders have obliquely-extending "thrust levers" which contact the wood after the cutting edge has entered it and force the spreaders to pivot and, in turn, force apart the wood.
U.S. Pat. No. 4,440,205 discloses a splitting tool which more or less combines the features of the prior patents. Thus, the splitting tool disclosed in this patent uses both spreaders that are forced apart by impact and which have thrust levers to force them apart.
The splitting tools disclosed in all of these patents, however, require substantial penetration of the wood by a cutting edge before the spreaders can operate to force the pieces of wood apart, and therein lies the problem. The tool needs to be swung against the wood with a great deal of force, or the cutting edge will not penetrate far enough for the spreaders to be effective. This can become very tiring to the person splitting the wood, since the benefit of the spreaders is not obtained except at great effort, thus reducing the advantages of having spreaders in the first place. In addition, unless the tool is swung against the wood hard enough for the spreaders to work, the cutting edge can bind in the wood, making splitting a difficult, tiring and time-consuming task.
One attempt at avoiding the problems with the prior tools is exemplified by U.S. Pat. No. 4,381,809. That patent discloses a splitting ax with a clamshell-type head which pivots open upon impact with the wood under the force of a movable wedge within the head. The halves of the head are spring-biased to automatically close when the ax is removed from the wood. The tool of that patent, however, also has to be swung against the wood with a great deal of force, or the wedge will not have enough impact momentum to force open the halves of the head. In addition, the tool is subject to binding because the wedge tends to keep the halves of the head in tight frictional contact with the wood on either side of the head. The wedge cannot be easily retracted to allow the head to close in order to eliminate binding.
There is a need for a simple, effective splitting tool that is effective without requiring a great deal of impact force to achieve splitting, is easy to use, simple to manufacture, and avoids the drawbacks of prior splitting tools. The present invention fulfills that need.